Abstract

Pediatric Research (1994) 36, 680–680; doi:10.1203/00006450-199411000-00070

12 HYPOTHYROIDISM NEONATAL SCREENING IN CORD BLOOD, EVALUATION OF 2 TSH ASSAYS

L P Gruñeiro1, L Bernal1, A Chiesa1, M G Ropelato1 and C Bergadá1

1Fundación de Endocrinologia Infantil. Hosp. ricardo Gutiérrez, División Endocrino. Buenos Aires, Argentina.

Top

Abstract

Cord blood neonatal screening for congenital hypothyroidism was carried out from October 1991 to December 1992 in Maternidad Ramón Sardá. It has been determined by TSH RIA. A total of 7365 dried blood samples from newborns were tested. Two hypothyroids (incidence 1:3682)and 2 transient hypothyroids(incidence 1: 3682) and 6 false positives (with TSH between 30 and 50 uU/ml) were detected. The recall rate was 0.14%versus 0.04%that is the rate we have in our screening after 48 hs of life. In order to decrease the recall rate in cord blood 76 samples from newborns were tested in parallel with RIA (DPC) and IRMA (ICN). The interassay coefficients of variation of RIA and IRMA were 20% and 5%, with a detection limit of 25 uU/ml and 2.5 uU/ml respectively. Distribution of TSH concentration (uU/ml) determined by RIA and IRMA was a follows:

RIA results were lower than IRMA(p< 0.001)(Wilcoxon's test). No correlation was found between the 2 mothods (r:0.13 Spearman rank). We suggest that IRMA neonatal assay represents a true alternative to RIA and has better sensitivity and specificity for cord blood samples allowing to decrease false positive results.